How do I allow spaces in this regex?

Question

I\'m such an amateur at regex, how do I allow spaces(doesn\'t matter how many) in this regex?

if(preg_match(\'/[^A-Za-z0-9_-]/\', $str)) return FALSE;


        

Answer 1

the \s in the regular expretion like this '/[^A-Za-z0-9_-\s]/'
mean the space

Answer 2

Not so much an answer to your question, but a site I find useful for checking regex expressions. It also explains what each part of the expression does / means as you hover over it in the input field.

Answer 3

You only need to add a literal blank space in your negated character class.

It would be more concise to use:

• the case-insensitive flag i and omit one of the letter ranges
• and write [0-9] as \d

like this:

if (preg_match('/[^A-Z0-9_ -]/i', $str)) return FALSE;

but even better would be to use \w which represents [A-Za-z0-9_] (which is most of your pattern) to write:

if (preg_match('/[^\w -]/', $str)) return FALSE;

This pattern states that if $str contains any character not in [A-Za-z0-9_ -] then false will be returned.

Answer 4

If you need to ALLOW only space you'll need '/ /'

If you need to ALLOW any whitespace char (space, tab, newline) - use '/\s/'

And if you need to add a space to your pattern (means to ignore space) - use /[^A-Za-z0-9_\ -]/

Answer 5

Your question is unclear. The regular expression, as it stands, will succeed if $str has any character in it that is not A-Za-z0-9_-. Since a space is not one of these characters, the regular expression will match, and the whole statement returns FALSE.

If this isn't what you want, and you want your regular expression to match if $str has any character that is not in A-Za-z0-9_- or a space, then you need to change it to A-Za-z0-9_ - (note the space between the underscore and the hyphen). Thus when your string has a character that is not A-Za-z0-9_ -, the regular expression will match, and your statement will return FALSE. If your string is made up entirely of A-Za-z0-9_ -, then the regular expression will fail to match, and your processing will continue to the next line.

Edit: Here's an example: If your string is abc123def, currently the regular expression will not match and you will not return FALSE. If your string is abc123 def, the regular expression will match and the statement will return FALSE. If you change the character class to A-Za-z0-9_ -, then the regular expression will fail to match for both abc123def and abc123 def, and you will not return FALSE.

Answer 6

if(preg_match('/[^A-Za-z0-9_ -]/', $str)) return FALSE;

Note that I put the space before the hyphen. If the space were after the hyphen, I would be specifying a character range from underscore to space. (Issue also evadable by putting a backslash before the hyphen to escape it.)

This is assuming that what you mean by "allow" is: this regex is being used to validate a character string, and if it matches, then the character string is disallowed (hence return FALSE). So the characters in the negated character class ([^...]) are actually the allowed characters. (This is causing some general confusion in this question.)